There is little chance that Department of Defense civilian employees will be able to avoid unpaid time off slated for this summer, federal officials said today.

Only a few types of highly essential workers — such as those maintaining nuclear submarines — will be exempt from the 11 days of furloughs announced, two senior officials said during a briefing at the Pentagon.

Most of the remaining 800,000 civilian employees will be forced to take one day of unpaid leave per week beginning July 8. Uniformed military personnel are exempt.

The unpaid leave is designed to save $1.8 billion as part of the $37 billion in cuts mandated by the sequester earlier this year.

The Defense Department will send letters between May 28 and June 5 to affected employees, who will have seven days to respond to their superiors. In theory they can make the case for why their job is essential, and local officials have some discretion.

But a senior defense official said that, in practice, few workers will be given a reprieve.

“This is a very, very tough decision,” she said. “We understand that it will create financial hardships across the board. But that is not a sheer reason for exempting (an employee) from a furlough.”

The two officials spoke only on background to avoid upstaging Defense Secretary Chuck Hagel, who held a town hall meeting earlier in the day on the same subject.

In a memo to top Pentagon officials released today, Hagel said the furloughs would be imposed in “every military department as well as almost every agency.” Some departments, such as the Navy, had hoped to be spared, but Hagel argued it is better to evenly spread the pain.

Exactly how the furloughs will be implemented is being left to local officials. Commissaries may be closed on a specific day so that other workers know to pack a lunch, while hospitals may rotate shifts with reduced staff. Furloughs for schoolteachers at military bases won’t begin until next fall to ensure students meet standards for days in the classroom.

The furloughs come as a last resort, the officials said. The sequester called for across-the-board cuts because it was supposed to be unpleasant enough to force Congress to agree to a better budget deal, a strategic move that backfired.

That left Pentagon accountants without much flexibility when it came time to implement the cuts.

The Army already has canceled rotations at its combat training centers, while the Air Force has reduced the number of combat squadrons. Routine maintenance is halted, and ceremonial activities such as performances by the Blue Angels air demonstration team are canceled.

“We kept going back. And finally, we got to a point where I could not responsibly go any deeper into cutting or jeopardizing our formations, our readiness and training,” Hagel said at the town hall meeting in Alexandria, Va., today.

The furloughs are an improvement over earlier predictions, however. The department originally had anticipated 22 days of unpaid leave, then later reduced that to 14.

If other military spending comes in under budget before the end of the fiscal year, some of the 11 days of furloughs may be canceled, though Hagel warned that it was not likely at this point.

The future remains uncertain for civilian employees of the military.

The plan outlined by Hagel still needs approval from Congress, although that is expected. President Obama’s budget for next year includes a 1 percent pay raise, but that depends on Congress passing a budget through the regular process — something it hasn’t done since 2009.

Another senior official said that most of the civilian employees work around the country.

“These people aren’t doing PowerPoint slides in the Pentagon,” he said. “They fix our ships, our tanks, our planes. They staff our hospitals, they’re teachers in our schools. … I think we will seriously adversely affect the productivity in almost all support areas of the Department of Defense.